Now they have improved the tools and increased support for the growing Machinima creators and the work is outstanding.
They, the second life folks, held a session recently on exactly that. So far it looks like the most active actual DOER amongst us training professionals is John Hartman aka Thought Plasma inwold. His blog under the same name is at thoughtplasma.com. In the blogosphere, when are Scobleized, you've done something right.
Some amazingly creative people are using SecondLife in amazing ways. Starwood Previews New Hotel Brand in Second Life. Or how about the New Media Center's SecondLife campus. Check out the SecondLife Creativity blog for more 2L goodness.
I can only answer the question in the title of this blog post with the following quote:
"Nobody can tell you what the Matrix is, you have to experience it for yourself." ~ Morpheus, The Matrix
UPDATE: Don't forget about the awesome wiki resource for Educators and Training Specialists.